1. Field of the Invention
The present invention relates to a liquid crystal display element having a transparent electrode substrate excellent in optical isotropy, smoothness, durability, chemical or solvent resistance, water moisture barrier properties, gas barrier properties, flexibility and so on. The present invention also relates to such a transparent electrode substrate, which is suitable not only for a liquid crystal display (LCD) element, but also for a touch panel, a photosensitive conductor, a planar phosphor, an organic electroluminescence element or the like.
2. Description of the Related Art
Recently, portable information apparatus such as a pager, a portable telephone, an electronic notebook and a portable information terminal have become popular and the business and the life style are going to be dorastically changed. To improve the portability of the information apparatus, it is demanded to make the information apparatus thinner, lighter and more durable.
Conventionally, a glass substrate which is heavy, thick and fragile has been used for a transparent electroconductive substrate of an LCD element or a touch panel. As an alternate material, a transparent resin substrate has been proposed, and the transparent resin substrate is advantageous in decreasing cost for manufacturing an LCD and the like since it can be processed in a roll-to-roll system. However, the transparent resin substrate is inferior to the glass substrate in durability, chemical or solvent resistance, gas barrier properties and other basic properties.
For example, in the case of a transparent resin substrate used as an electrode for a LCD element, the gas barrier property can be improved by providing a metal oxide layer to the transparent resin substrate. However, there are problems that in the step of removing a resist after patterning the transparent electrode, the metal oxide layer contacts an alkali solution by which the metal oxide layer is dissolved, and in the step of forming a liquid crystal alignment layer, a coating composition for the liquid crystal alignment layer containing N-methylpyrolidone or other solvent is used and the transparent resin substrate in contact with the solvent is damaged or, for example, becomes white or swollen.
To solve the above problems, there are some proposals of laminating a layer having a gas barrier property and a chemical resistance onto the transparent resin substrate. For example, Japanese Examined Patent Publication (Kokoku) Nos. 5-52002 and 5-52003 propose a transparent substrate comprising a polymer film and an oxygen gas barrier layer made of polyvinyl alcohol which has an improved adhesivity and further a moisture barrier property. However, the polyvinyl alcohol-based polymer layer disposed as the outermost layer does not have a sufficient chemical resistance and therefore causes problems during manufacturing a liquid crystal cell. The chemical resistance may be given by additionally providing a chemical resistant layer, which however increases the cost.
Japanese Unexamined Patent Publication (Kokai) Nos. 2-137922 and 5-309794 propose a transparent substrate comprising a transparent polymer film, an anchor layer, a gas barrier layer made of ethylene-vinyl alcohol copolymer and a solvent-resistant layer in this order as a stack. In this transparent substrate, the solvent-resistance is satisfactory but the gas barrier property at a high humidity is lowered due to the property of the material of the gas barrier layer, and the structure of the six layers increases manufacturing cost.
Further, in a transparent substrate of a liquid crystal display element, the following demands on and problems of the properties exist in addition to the above chemical resistance and gas barrier properties.
If the substrate is low in its transparency or has a birefrigence, the coloring of the display and lowering of contrast occur.
If the surface smoothness of the substrate is low, the gap for a liquid crystal layer becomes non-uniform and the liquid crystal orientation may be disordered or the substrate may become optically non-uniform. As a result, the displaying color becomes non-uniform.
Moreover, if the smoothness, transparency, and gas barrier properties of the substrate are deteriorated by mechanical or thermal influence or by contact with a solvent, the advantages of the lightness, the wide range of the freedom of shape and the possibility of a curved display can not be obtained in applications to a pager, a portable telephone, an electronic notebook, a pen-input apparatus and so on since they receive substantial outer mechanical or thermal influences. In particular, considering the resistance to the mechanical influence, excellent adhesion between the layers is required to maintain the above advantageous properties.
The object of the present invention is to provide a liquid crystal display element having a transparent resin substrate which is excellent in the chemical or solvent resistance, gas barrier properties, transparency, smoothness, adhesivity and so on as mentioned above and which has a small number of laminated layers and thus is low in manufacturing cost.